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Android Testing Strategy Marcelo Benites

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Why is it so hard to test an Android application?

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No access to Android components constructor (Activity, Service, Application, Content Provider and Broadcast Receiver).

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It is hard to fake Android OS events during testing (Battery Level, Location, Sensors etc...).

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Android emulator is slow.

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How do we solve those problems?

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Clean Architecture

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Domain ● Business Logic ● No implementation details (HTTP, SQLite, Bluetooth, etc...) ● No external dependencies (including Android SDK)

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Data ● Simple adapter to a data source: Http, File System, Bluetooth, WebSocket, Push etc... ● Should not be complex. Move complexity to the Domain ● No external dependencies (including Android SDK)

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Presentation ● Presenter, Controller, ViewModel ● No external dependencies (including Android SDK)

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External Dependencies ● Android SDK ● RxJava, Fragment, Activity, Room, Retrofit, OKHttp, Dagger, etc...

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Controller Presenter Use Case Implementation Callback Use Case Flow of control Domain Gateway Gateway Implementation Data Presentation

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Testing Strategy

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Testing Strategy ● Unit Tests - Test Presentation, Domain and Data in isolation. ● Integration Tests - Test Data and Presentation interaction with External Dependencies. ● Component Tests - Test Presentation, Domain and Data interaction using Test Doubles (Mock, Fake, Spy, Stub) for External Dependencies. ● End-to-End Tests - Test Presentation, Domain Data and External Dependencies interaction.

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Show me the code!

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Conference Application

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BDD

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As a user I want to see conference details

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Given a conference is registered with name Droidcon When I open conference application Then I see Droidcon on the screen

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TDD

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Unit Tests Domain Data Presentation

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Domain First!

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State

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data class State( val name: Name, val value: T? = null ) { enum class Name { IDLE, LOADING, LOADED, ERROR } } Idle Loading Loaded Error

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Threading

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interface Dispatcher { fun dispatch(execute: () -> Unit, error: (Throwable) -> Unit) fun dispatch(execute: () -> Unit) }

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Data Contract

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interface ConferenceGateway { fun getConference(): Conference } data class Conference(val id: String, val name: String)

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Arrange, Act, Assert

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Arrange

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@Test fun `Given a registered conference When start is called Then should emit loaded state with conference`() { val conference = Conference("1", "Droidcon") val stateMachine = ConferenceStateMachine( FakeDispatcher(), FakeConferenceGateway(conference) ) val listenerMock = mockk<(State) -> Unit>() stateMachine.addStateChangedListener(listenerMock) stateMachine.start() verifyOrder { listenerMock.invoke(State(State.Name.LOADING)) listenerMock.invoke(State(State.Name.LOADED, conference)) } }

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Act

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@Test fun `Given a conference When start is called Then should emit loaded state with conference`() { val conference = Conference("1", "Droidcon") val stateMachine = ConferenceStateMachine( FakeDispatcher(), FakeConferenceGateway(conference) ) val listenerMock = mockk<(State) -> Unit>() stateMachine.addStateChangedListener(listenerMock) stateMachine.start() verifyOrder { listenerMock.invoke(State(State.Name.LOADING)) listenerMock.invoke(State(State.Name.LOADED, conference)) } }

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Assert

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@Test fun `Given a conference When start is called Then should emit loaded state with conference`() { val conference = Conference("1", "Droidcon") val stateMachine = ConferenceStateMachine( FakeDispatcher(), FakeConferenceGateway(conference) ) val listenerMock = mockk<(State) -> Unit>() stateMachine.addStateChangedListener(listenerMock) stateMachine.start() verifyOrder { listenerMock.invoke(State(State.Name.LOADING)) listenerMock.invoke(State(State.Name.LOADED, conference)) } }

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Test fails!

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Make it pass.

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class ConferenceStateMachine( private val conferenceGateway: ConferenceGateway, private val dispatcher: Dispatcher ) : StateMachine() { override fun start() { loadConference() } private fun loadConference() { dispatcher.dispatch({ moveToLoading() moveToLoaded(conferenceGateway.getConference()) }, { moveToError(it) }) } }

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Presentation

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MVP (for the sake of simplicity)

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View Contract

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interface ConferenceView { fun hideLoading() fun showLoading() fun hideError() fun showError() fun showConferenceName(name: String) fun hideConferenceName() }

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Arrange

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@Test fun `Given a loaded conference When state is updated Then show conference name`() { val view = mockk() val presenter = ConferencePresenter(FakeDispatcher(), view) presenter.invoke(State(State.Name.LOADED, Conference("1", "Droidcon"))) verify { view.hideError() view.hideLoading() view.showConferenceName("Droidcon") } }

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Act

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@Test fun `Given a loaded conference When state is updated Then show conference name`() { val view = mockk() val presenter = ConferencePresenter(FakeDispatcher(), view) presenter.invoke(State(State.Name.LOADED, Conference("1", "Droidcon"))) verify { view.hideError() view.hideLoading() view.showConferenceName("Droidcon") } }

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Assert

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@Test fun `Given a loaded conference When state is updated Then show conference name`() { val view = mockk(relaxed = true) val presenter = ConferencePresenter(FakeDispatcher(), view) presenter.invoke(State(State.Name.LOADED, Conference("1", "Droidcon"))) verify { view.hideError() view.hideLoading() view.showConferenceName("Droidcon") } }

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Data

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Integration Tests Data Fake DB Fake External Service

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Arrange

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OkHttp and MockWebServer

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@Test fun `When conference is requested Then call conference endpoint with GET method`() { val server = MockWebServer() server.start() val baseUrl = server.url("/").toString() val gateway = OkHttpConferenceGateway(baseUrl, OkHttpClient()) val json = """ { "id": "1", "name": "Droidcon" } """ server.enqueue(MockResponse().setResponseCode(200).setBody(json)) val conference = gateway.getConference() assertEquals(Conference("1", "Droidcon"), conference) val request = server.takeRequest() assertEquals("GET", request.method) assertEquals("/conference", request.path) server.shutdown() }

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Act

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@Test fun `When conference is requested Then call conference endpoint with GET method`() { val server = MockWebServer() server.start() val baseUrl = server.url("/").toString() val gateway = OkHttpConferenceGateway(baseUrl, OkHttpClient()) val json = """ { "id": "1", "name": "Droidcon" } """.trimIndent() server.enqueue(MockResponse().setResponseCode(200).setBody(json)) val conference = gateway.getConference() assertEquals(Conference("1", "Droidcon"), conference) val request = server.takeRequest() assertEquals("GET", request.method) assertEquals("/conference", request.path) server.shutdown() }

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Assert

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@Test fun `When conference is requested Then call conference endpoint with GET method`() { val server = MockWebServer() server.start() val baseUrl = server.url("/").toString() val gateway = OkHttpConferenceGateway(baseUrl, OkHttpClient()) val json = """ { "id": "1", "name": "Droidcon" } """.trimIndent() server.enqueue(MockResponse().setResponseCode(200).setBody(json)) val conference = gateway.getConference() assertEquals(Conference("1", "Droidcon"), conference) val request = server.takeRequest() assertEquals("GET", request.method) assertEquals("/conference", request.path) server.shutdown() }

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Component Tests Domain Data Fake DB Fake External Service Presentation Fake GUI

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Dependency Injection

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interface DependencyManager { val conferenceStateMachine: StateMachine val mainDispatcher: Dispatcher } interface ViewContainer { val dependencyManager: DependencyManager }

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class TestActivity : AppCompatActivity(), ViewContainer { var testDependencyManager: DependencyManager? = null override val dependencyManager: DependencyManager by lazy { testDependencyManager!! } override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) val view = LinearLayout(this) view.id = 1 setContentView(view) } fun showFragment(fragment: Fragment) { supportFragmentManager .beginTransaction() .replace(1, fragment) .commit() } }

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class TestActivity : AppCompatActivity(), ViewContainer { var testDependencyManager: DependencyManager? = null override val dependencyManager: DependencyManager by lazy { testDependencyManager!! } override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) val view = LinearLayout(this) view.id = 1 setContentView(view) } fun showFragment(fragment: Fragment) { supportFragmentManager .beginTransaction() .replace(1, fragment) .commit() } }

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@RunWith(AndroidJUnit4::class) class ConferenceComponentTest { @get:Rule val rule: ActivityTestRule = ActivityTestRule(TestActivity::class.java) @Test fun `Given a registered conference When conference screen appears Then show conference name`() { val server = MockWebServer() server.start() val baseUrl = server.url("/").toString() val json = """ { "id": "1", "name": "Droidcon" } """ server.enqueue(MockResponse().setResponseCode(200).setBody(json)) val stateMachine = ConferenceStateMachine(OkHttpConferenceGateway(baseUrl, OkHttpClient()), FakeDispatcher()) stateMachine.start() rule.activity.testDependencyManager = FakeDependencyManager(stateMachine, FakeDispatcher()) rule.activity.showFragment(ConferenceFragment()) onView(withId(R.id.conferenceName)).check(matches(ViewMatchers.withText("Droidcon"))) server.shutdown() } }

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Arrange

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@RunWith(AndroidJUnit4::class) class ConferenceComponentTest { @get:Rule val rule: ActivityTestRule = ActivityTestRule(TestActivity::class.java) @Test fun `Given a registered conference When conference screen appears Then show conference name`() { val server = MockWebServer() server.start() val baseUrl = server.url("/").toString() val json = """ { "id": "1", "name": "Droidcon" } """ server.enqueue(MockResponse().setResponseCode(200).setBody(json)) val stateMachine = ConferenceStateMachine(OkHttpConferenceGateway(baseUrl, OkHttpClient()), FakeDispatcher()) stateMachine.start() rule.activity.testDependencyManager = FakeDependencyManager(stateMachine, FakeDispatcher()) rule.activity.showFragment(ConferenceFragment()) onView(withId(R.id.conferenceName)).check(matches(ViewMatchers.withText("Droidcon"))) server.shutdown() } }

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Act

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@RunWith(AndroidJUnit4::class) class ConferenceComponentTest { @get:Rule val rule: ActivityTestRule = ActivityTestRule(TestActivity::class.java) @Test fun `Given a registered conference When conference screen appears Then show conference name`() { val server = MockWebServer() server.start() val baseUrl = server.url("/").toString() val json = """ { "id": "1", "name": "Droidcon" } """ server.enqueue(MockResponse().setResponseCode(200).setBody(json)) val stateMachine = ConferenceStateMachine(OkHttpConferenceGateway(baseUrl, OkHttpClient()), FakeDispatcher()) stateMachine.start() rule.activity.testDependencyManager = FakeDependencyManager(stateMachine, FakeDispatcher()) rule.activity.showFragment(ConferenceFragment()) onView(withId(R.id.conferenceName)).check(matches(ViewMatchers.withText("Droidcon"))) server.shutdown() } }

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Assert

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@RunWith(AndroidJUnit4::class) class ConferenceComponentTest { @get:Rule val rule: ActivityTestRule = ActivityTestRule(TestActivity::class.java) @Test fun `Given a registered conference When conference screen appears Then show conference name`() { val server = MockWebServer() server.start() val baseUrl = server.url("/").toString() val json = """ { "id": "1", "name": "Droidcon" } """ server.enqueue(MockResponse().setResponseCode(200).setBody(json)) val stateMachine = ConferenceStateMachine(OkHttpConferenceGateway(baseUrl, OkHttpClient()), FakeDispatcher()) stateMachine.start() rule.activity.testDependencyManager = FakeDependencyManager(stateMachine, FakeDispatcher()) rule.activity.showFragment(ConferenceFragment()) onView(withId(R.id.conferenceName)).check(matches(ViewMatchers.withText("Droidcon"))) server.shutdown() } }

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End-to-End Tests Domain Data Presentation DB External Service Android SDK

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Arrange

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Act

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@RunWith(AndroidJUnit4::class) class ConferenceEndToEndTest { @get:Rule val rule: ActivityTestRule = ActivityTestRule(MainActivity::class.java, true, false) @Test fun givenRegisteredConferenceWhenApplicationStartsStartShowConferenceName() { rule.launchActivity(Intent()) Thread.sleep(2000) onView(ViewMatchers.withId(R.id.conferenceName)).check(matches(withText("Droidcon"))) } }

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Assert

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@RunWith(AndroidJUnit4::class) class ConferenceEndToEndTest { @get:Rule val rule: ActivityTestRule = ActivityTestRule(MainActivity::class.java, true, false) @Test fun givenRegisteredConferenceWhenApplicationStartsStartShowConferenceName() { rule.launchActivity(Intent()) Thread.sleep(2000) onView(ViewMatchers.withId(R.id.conferenceName)).check(matches(withText("Droidcon"))) } }

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Unit Tests Integration Tests Component Tests End-to-End Tests Domain Data Fake DB Fake External Service Presentation Fake GUI DB External Service Android SDK

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Reference ● The Clean Architecture - Robert Martin (http://blog.cleancoder.com/uncle-bob/2012/08/13/the-clean-architecture.html) ● Test Double - Martin Fowler (https://martinfowler.com/bliki/TestDouble.html) ● Testing Strategies in a Microservices Architecture - Martin Fowler (https://martinfowler.com/articles/microservice-testing/#conclusion-summary) ● Managing State with RxJava - Jake Wharton (https://www.youtube.com/watch?v=0IKHxjkgop4) ● Android Testing Strategy - Marcelo Benites (https://engineering.talkdesk.com/android-testing-strategy-73269539c13d)

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https://github.com/marcelorbenites/android-testing-strategy